A novel stepwise catheter ablation method of the mitral isthmus for persistent atrial fibrillation: efficacy and reproducibility

Abstract

Background: Ethanol infusion of the vein of Marshall (EI-VOM) has been widely used to facilitate mitral isthmus (MI) ablation. According to the literature, the success rate of achieving a bidirectional conduction block across the MI ranges from 51 to 96%, with no standardized strategy or method available for cardiac electrophysiologists.

Objectives: This study aimed to introduce and evaluate a novel ablation method of MI.

Methods: Consecutive patients with persistent atrial fibrillation (PeAF) that underwent catheter ablation were included. The MI ablation procedure followed a stepwise approach. In step 1, ethanol infusion of the vein of Marshall (EI-VOM) was performed. In step 2, a "V-shape" endocardial linear ablation connecting the left inferior pulmonary vein (LIPV) to mitral annulus (MA) was performed. In step 3, earliest activation sites(EASs) near the ablation line were identified using activation mapping followed by reinforced ablation. In step 4, precise epicardial ablation was performed, with the catheter introduced into the coronary sinus(CS) to target key ablation targets (KATs).

Results: 135 patients with PeAF underwent catheter ablation with the stepwise ablation method adopted in 119 cases. Bidirectional conduction blocks were achieved in 117 patients (98.3%). The block rates of every step were 0%, 58.0%, 44.0%, and 92.9%, and the cumulative block rates for the four steps were 0%, 58.0%, 76.5%, and 98.3%, respectively. No patient experienced fatal complications.

Conclusions: Our novel stepwise catheter ablation method for MI yielded a high bidirectional block rate with high reproducibility.

Keywords: Catheter ablation; Ethanol infusion of the vein of Marshall; Mitral isthmus ablation; Persistent atrial fibrillation.

Fig. 1

Endpoint of the mitral isthmus (MI) ablation. (A) Before ablation, the coronary sinus (CS) catheter recorded a CS1-2 to CS 9–10 activation sequence when pacing at the Left atrial appendage (LAA) by the Pentaray catheter (left). After ablation, the activation sequence was transformed into CS9-0 to CS1-2 (right); (B) Before ablation, the ablation catheter recorded a 1–2 to 3–4 activation sequence when pacing at the distal of the CS catheter (left). After ablation, the activation sequence was transformed into 3–4 to 1–2 (right)

Fig. 2

Ethanol infusion of the vein of Marshall (EI-VOM) and marked VOM ostium(red arrow)

Fig. 3

Endocardial “V-shape” linear ablation of the mitral isthmus (MI). The upper ablation line was closed to the root of the Left atrial appendage(LAA) from the 1–2 o’clock point of the mitral annulus at the Left anterior oblique (LAO) 45º view to the left inferior pulmonary vein(LIPV), closing to the root of LAA. The lower ablation line coursed from the LIPV to the lower MA anatomically corresponding to the ostium of the vein of Marshall (VOM)

Fig. 4

Activation mapping and reinforced ablation of the earliest activation sites (EASs). (A) The EASs around the upper line of the “V-shape” ablation were identified, and reinforced ablation was performed; (B) The EASs around the lower line were identified, and reinforced ablation was performed

Fig. 5

An earlier epicardial activation than the endocardium. activation sequence on CS1-2 (epicardium) was earlier than MAP1-2(endocardium) when ablating earliest activation sites (EASs).

Fig. 6

Precise epicardial ablation in the coronary sinus(CS). (A) The activation sequence was from distal to proximal CS catheter before epicardial ablation. (B) The activation sequence reversed after precise epicardial ablation pointing to the endocardial earliest activation sites (EASs) anatomically in CS.